A case of pencil-core granuloma

A 44-year-old man had noted brownish blue eruption more than 10 year before in the right great toe. The eruption had enlarged gradually together with pain. We surgically removed the skin change under local anesthesia. While he did not recall whether pencil stuck in the toe or not, we histopathologically diagnosed him as pencil-core granuloma. Pencil-core granuloma is a foreign body granuloma against pencil lead, and is usually observed as blue or black subcutaneous tumor. It is rapidly enlarged several years or decades after the prick with the pencil lead. Similar to our case, patients occasionally have no recollection of the prick. Since the rapid enlargement and blue or black color of the pencil-core granuloma, we should carefully differentiate it from malignant melanoma and malignant blue nevus.